1. FIELD OF THE INVENTION
The present invention relates to seismic sources.
2. DESCRIPTION OF THE PRIOR ART
Certain prior art seismic sources for geophysical or seismic exploration beneath land surfaces, such as that disclosed in U.S. Pat. No. 3,310,128, have been based on an attempt to adapt an air gun used in marine seismic surveying to land use. A large and cumbersome water-filled tank was mounted with a special form of truck bed to receive the air gun and couple the energy from the gun to the land surface at the seismic shot point or signal transmission point.
When the source was moved to a new shot point, the water tank was drained and raised from the ground, and the truck driven to a new shot point, making this exploration technique cumbersome, time consuming, and expensive.
Other apparatus, such as that disclosed in U.S. Pat. No. 3,435,410, mounted a "sparker" or electric spark discharge seismic source in partially liquid-filled tires for use as a seismic exploration source. A considerable portion of the energy from the sparker was consumed in compressing the air or gas remaining in the partiall liquid-filled tires. This was undesirable, due to the reduction in the energy output from the source.